The progress of a recent wireless technology is remarkable. Even if it is limited to a private usage, the technology for making the indoor telephone fully wireless became a reality with the use of a PBX private branch exchange) system, etc., based on the technique for personal communications which is a result of the development of cordless telephones. Moreover, a wireless LAN (local area network) is widely practiced also in the field of data communications. This LAN undertakes a role for making offices and the like wireless.
In the wireless PBX, mobility, as well as wireless of telephones, was pursued. That is, a movement in the wireless area under the control of a single PBX is made possible as a matter of course, and in addition, even a movement across between PBX is also made possible by the automatic position registration, without compelling the user a useless registration change (or, transmitting an incoming signal, etc.). This technology is often referred to as "loaming between PBX". In principle, it realizes a possibility of endless movement even within the private branch. Moreover, a PBX added-service based on the use of the PBX which mostly uses the voice is realized in an almost perfect shape with the realization of this mobility.
On the other hand, recently, needs to a telephoneless communication as represented by e-mail have been increasing. This telephoneless communication method includes a method for performing a communication through a telephone line (channel exchange) and a method for performing a communication from a terminal equipment accommodated within the LAN. Needless to say, the method using the LAN is chiefly employed in recent offices. In addition, the appearance of the Internet is spurring the popularization of this LAN further. Now, the technology of the Internet is briefly described.
The Internet is one embodied form of a virtual network which aims at performing worldwide communications across the various physical networks represented by LAN such as Ethernet, essentially satisfying the following items.
(a) The network principle of the Internet is to realize a virtual network and not to specify a form of realization of a physical network.
(b) The Internet address does not obligate the existence of a switching node which performs the switching intensively. On the other hand, it is necessary for the terminal equipment to be fixed to the physical network.
In order to perform a routing between the terminal equipments across the various physical networks, it is necessary that the terminal equipments are uniquely identified in the world. Concretely, it is necessary that a connection point with the physical network where the specific terminal equipment is accommodated is uniquely identified in the world. In the Internet, therefore, an address called "IP (Internet Protocol) address" is assigned to each terminal equipment based on a common system in the world, and the routing is performed based on this Internet Protocol address.
The wireless PBX chiefly comprising the channel exchange and the Internet based on the LAN were explained hereinbefore. The former is becoming main communication means in offices by adding mobility thereto, and the latter is becoming main communication means for data communications. It seams that importance of those communication means will rise more and more as a basic structure for supporting activities in offices in the future.
By the way, in the virtual network across the wireless PBX and the LAN, the data communication terminal equipment, which is under the control of the wireless PBX, occasionally transmits packet data. In such occasions, a communication channel in the wireless PBX system was established by signal outputted from the telephone (personal station) connected to the data communication terminal equipment, and a data communication was performed via the LAN. That is, the role to make the address on the virtual network and the address (in this case, telephone number) on the physical network correspond to each other was played by man as an addresser of the data. Therefore, the operation was troublesome.